<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
            list-style: none;
        }

        .box {
            margin: 50px;
        }

        li {
            width: 150px;
            height: 20px;
            margin: 10px 0;
            overflow: hidden;
        }

        p {
            width: 0;
            height: 100%;
        }

        @keyframes one {
            to {
                width: 100%;
            }
        }

        li:first-child {
            background-color: rgb(209, 209, 209);
        }

        li:first-child p {
            background-color: #000;
            animation: one 3s infinite;
        }

        @keyframes two {
            to {
                width: 100%;
            }
        }

        li:nth-child(2) {
            border-radius: 10px;
        }

        li:nth-child(2) p {
            background: linear-gradient(to right, rgb(244, 135, 153), rgb(121, 210, 246));
            animation: two 3s infinite;
        }

        @keyframes three {
            to {
                width: 100%;
            }
        }

        li:nth-child(3) {
            border-radius: 10px;
            background: repeating-linear-gradient(50deg, rgb(221, 221, 221) 0px 10px, rgb(233, 233, 233) 10px 20px);

        }

        li:nth-child(3) p {
            background: repeating-linear-gradient(50deg, rgb(254, 26, 26) 0px 10px, rgb(252, 172, 24) 10px 20px);
            animation: three 3s infinite;
        }


        @keyframes four {
            to {
                background-size: 120%;
            }
        }

        li:nth-child(4) {
            width: 120px;
            background:
                repeating-linear-gradient(to right, #000 0px 20px, #fff 0px 25px) 0/0% no-repeat,
                repeating-linear-gradient(to right, rgb(211, 211, 211) 0px 20px, #fff 0px 25px) 0/100%;
            animation: four 3s steps(6) infinite;
        }

        li:nth-child(5) {
            width: 120px;
            background: repeating-linear-gradient(to right, rgb(211, 211, 211) 0px 15px, #fff 0px 20px) 0/100%;
        }

        li:nth-child(5) p {
            width: 100%;
            background: repeating-linear-gradient(to right, #000 0px 15px, #fff 0px 20px) 0/0% no-repeat;
            animation: five 3s steps(7) infinite;
        }

        @keyframes five {
            to {
                background-size: 117%;
            }
        }
    </style>
</head>

<body>
    <div class="box">
        <ul>
            <li>
                <p></p>
            </li>
            <li>
                <p></p>
            </li>
            <li>
                <p></p>
            </li>
            <li></li>
            <li>
                <p></p>
            </li>
        </ul>
    </div>
</body>

</html>